Bizarre may never work on another Project Gotham Racing game again, what with their defection to Activision, but they're no fools. They knew what made the series tick, and made steps to protect that investment. So while Microsoft own the name Project Gotham Racing, they don't own the series' trademark Kudos system. Bizarre's Sarah Chudley explains:

Gotham's owned by Microsoft. They will be doing with Gotham whatever they want...We still own the Kudos element. We have a joint patent with Microsoft, so that's something we could use in the future if we wanted to.